The invention relates to a control method and a control device for the operation of rotationally or linearly driven axes with a position control.
If, in addition to its drive movement, a rotationally or linearly driven axis is swiveled or moved onto a path or position, it performs an additional superposed movement. In the case of printing machines, for example, pressure rollers are pressed onto or lifted off a paper web. This is referred to as xe2x80x9cpressure onxe2x80x9d or xe2x80x9cpressure offxe2x80x9d. In this case, a drive experiences an additional turning motion in relation to its reference system. A measuring system, such as a rotary encoder, measures the movements in relation to the housing. This superposed movement is usually registered by an additional measuring system and fed to a control in order to compensate for the superposed movement. If this does not take place, it is possible in the case of the printing machine for tearing of the paper web to occur and consequently for there to be a breakdown of a production machine or production process.
The situation explained using the printing machine as an example is applicable to other production machines, machine tools or robots (hereinafter xe2x80x9cmachinesxe2x80x9d). Hence a movement additionally superposed in relation to the reference system can lead to a control error, which while compensated by a control device, may be undesired in the production process. Furthermore, an additional measuring system is required to register the superposed movement.
German patent application Number 101 256 09.4 has proposed a control method for the operation of individually driven rotating machine elements with an angular position control, which are coupled with frictional connection or via a common load. In this case, boundary-describing parameters of the driven, corresponding machine elements in the form of an angular position deviation are fed as a correcting quantity to the input of the angular position controller. This method does not make it possible to determine superposed movement components and remove them from the control information.
A rotary printing machine is described in the international application WO 97/11848. This generally comprises a plurality of producing units, known as rotary presses, which can operate simultaneously and independently of one another. Each producing unit comprises, inter alia roll carriers for the paper rolls, draw rollers for drawing the paper web in and out of the printing towers, printing stations, which operate in combination as U, Y or H printing units in one or more printing towers, auxiliary drives at the printing stations and the folder.
The object of the present invention is to determine specific, superposed movement components, the beginning and end of which are defined in terms of when they occur, from control or process information of rotationally or linearly driven axes without the need for additionally installed measuring systems, and eliminating the superposed movement components from the control. According to the present invention, this object is achieved by providing at least one setpoint position value and at least one actual position value of an axis or component to be controlled, and determining the difference between the setpoint position value and actual position value caused by an additional movement component during the time period of the occurrence of at least one superposed movement by subtraction of one value from the other, and with the additional movement component being eliminated from all the required control data paths. Accordingly, this control method advantageously makes it possible to (a) determine a superposed movement component during a known period of occurrence from the setpoint position value and the actual value, without additionally installed measuring systems, and (b) to remove it from the control or process information.
A preferred embodiment of the present invention is characterized in that a movement component known from the sequence of movements in the control is eliminated from all the required control data paths. Consequently, it is no longer necessary for the sequence of movements first to be determined and then to eliminate it from the required control data paths, relying instead on a known sequence of movements, which if need be may be stored in the control. It is also conceivable for this stored sequence of movements to be provided by an additional storage medium.
Another preferred embodiment of the present invention is characterized in that the known movement component occurs periodically during the time period of the superposed movement. In accordance with this method, it is only necessary to store one period of the known movement component.
Yet another preferred embodiment of the present invention is characterized in that a movement component which can be mathematically defined as desired is eliminated from all the required control data paths. As a result, it is possible for example to eliminate mean values of movement components or mathematical approximations of known sequences of movements from the control data paths.
In another preferred embodiment of the present invention at least one superposed movement component is eliminated from all the required control data paths using the aforesaid method and a position deviation is formed from the setpoint position value and actual position value, which is fed to a position controller; a rotational speed deviation is formed from a setpoint rotational speed and actual rotational speed, which is fed to a speed controller; a current deviation is formed from a setpoint current value and actual current value, which is fed to a current controller, with a torque to be required from the current controller being fed to an axis drive.
The present invention may be used in the case of a machine tool, production machine or a robot to eliminate a superposed movement component from the control data paths. In particular, where the production machine is a printing machine where a high-quality printed image is required, a swiveling movement of pressure rollers, as performed in the case of the xe2x80x9cpressure onxe2x80x9d and xe2x80x9cpressure offxe2x80x9d command, has the effect that an additional movement component is contained in the axis drive of the pressure roller. This is compensated by the drive control, which is usually operated with a position control. This may lead to tearing of the paper web and a breakdown of the printing machine or the entire printing process. Furthermore, registration of superposed movement components is made possible without additional measuring systems. This allows cost savings to be realized.